Ink jet printers having one or more ink jet heads for projecting drops of ink onto paper or other printing medium to generate graphic images and text have become increasingly popular. To form color images, multiple ink jet printing heads are used, with each head being supplied with ink of a different color from an associated ink cartridge.
In a common arrangement, the print medium is attached to a rotating drum, with the ink jet heads being mounted on a travelling carriage that traverses the drum axially. As the heads scan spiral paths over the medium, ink from the ink cartridges is delivered to the ink jet heads. Ink drops developed within the heads are projected from a minute orifice to form an image on the medium. A suitable control system synchronizes the generation of ink drops with the rotating drum.
Such printers commonly employ replaceable ink cartridges. One such known cartridge, designated the Maco cartridge, is produced by Matsushita Electronic Components Co., Ltd. of Japan. The Maco cartridge has an internal ink container which includes a collapsible ink bag and an ink bag support. The ink bag is an extruded tube of flexible polyvinylchloride which is thermally sealed at one end. The ink bag support is inserted in the open end of the bag and clamped in place by a mechanical seal. More specifically, the portions of the ink bag which bound the ink bag opening are wedged between the sides of the ink bag support and a surrounding rubber ink bag sealing gasket. The assembled ink bag, ink bag support and ink bag gasket are inserted into an elongated metal clip of U-shaped cross section with a planar base and sides which overlie the sides of the ink bag sealing gasket. This assembly is positioned within a plastic housing. A cap portion of the housing compresses the clip and ink bag sealing gasket to complete the mechanical seal. Also, a cap gasket is provided between the base of the clip and the cap for seaing purposes. Furthermore, fasteners extend through the cap, the cap gasket, openings in the clip, and into corresponding bosses projecting toward the cap from the ink bag support to hold the assembled cartridge together.
The Maco cartridge ink bag support includes an annular projection which defines an ink flow passageway which communicates with the interior of the ink bag. This projection passes through the clip base, abuts one side of the cap sealing gasket, and is aligned with an ink flow port through the cap. When the cap gasket is punctured, ink may flow from the ink bag, through the ink flow passageway, the cap gasket and ink flow port and thereby from the cartridge to an ink jet head. In addition, an annular air flow passageway defining projection ink extends from the ink bag support, through an opening in the clip base, and against the cap gasket. This air flow passageway is aligned with an air flow port through the cap. The air flow passageway has openings which communicate with the interior of the housing outside of the ink bag. When the cap gasket is punctured, air or other fluid under pressure may be delivered through the air flow passageway and into the housing, wherein it applies pressure to the ink bag. This urges ink from the ink bag through the ink flow passageway.
This Maco cartridge construction suffers from a number of disadvantages. For example, cartridges are used in environments where they are subject to being dropped or otherwise impacted. Prior cartridges, such as the Maco cartridge, tend to develop ink leaks when jarred in this manner. Leakage also is a problem when such known cartridges are subjected to substantial environmental temperature fluctuations. Also, leakage of the air pressure surrounding the ink bag is a problem when the cartridge housing is exposed to its own ink, both from the interior and exterior, especially at its solvent bondlines. The result is polycarbonate case cracking and attendant leakage.
In addition, prior cartridges, such as the Maco cartridge, are costly and difficult to manufacture and assemble. In particular, it is difficult to remove air and other gases from the Maco ink bag, by applying a vaccum to the ink flow passageway, before filling the ink bag with ink. It is important to remove such gases from the ink bag to prevent clogging of the ink jet print heads by the gas bubbles from the ink container.
Therefore, a need exists for an ink cartridge apparatus which overcomes these and other disadvantages of the prior art.